The Internet provides promising terrain for the development and delivery of novel treatments for mental illness. The possibility of effective Internet-based interventions, which can incorporate the needs and circumstances of diverse populations outside traditional treatment settings, must be thoroughly explored. An existing treatment, Mindfulness-based Cognitive-behavioral Therapy (MBCT), significantly reduces relapse rates in recurrent depression among general adult samples, and an internet-delivered preventive intervention based on MBCT ("eMBCT") is in conceptual development. A study investigating the feasibility, safety, acceptability, and preliminary efficacy of eMBCT in preventing depressive relapse/recurrence, is proposed. The project involves 3 phases: 1) conceptualizing the intervention based on theory and empirical research;2) developing and standardizing the intervention, and 3) conducting an open trial to evaluate clinical and feasibility outcomes of eMBCT by assessing levels of depressive symptoms and proximal markers of relapse risk. Phase 1 will identify content domains, write learning objectives and list the specific mindfulness practices and depression awareness exercises contained in each of the 9 MBCT sessions that will form the backbone of eMBCT. In Phase 2, researchers at the Centre for Addiction and Mental Health, the University of Colorado at Boulder and Kaiser Permanente Colorado will work collaboratively with Allen Interactions, a leader in eLearning applications and custom web design, to develop a fully functional prototype of the eMBCT website. This process will be iterative and incremental, comprising the generation of web interactions and content and revisions of this material based on focus group and user testing with both patient and clinician/stakeholder samples (N=84). This will provide important data on eMBCT's usability, satisfaction, knowledge acquisition and acceptability. In Phase 3, a proof of concept open trial (N=50) with remitted depressed patients will be conducted. This trial will allow data gathering on the degree of patient engagement with eMBCT by comparing rates of attrition and homework compliance with indices reported for in-person MBCT groups. Pre and post treatment differences on depression scores and two variables shown to be strong predictors of relapse in other studies, namely rumination and degree of mindfulness, will also be examined. Given the negative, long-term, consequences of untreated relapse and recurrence risk in people recovering from depression, and the scarcity of MBCT resources in the community, the development of eMBCT has the potential to significantly benefit patients, their families, and society at large. PUBLIC HEALTH RELEVANCE: Relapse and recurrence following recovery from Major Depressive Disorder is a significant public health concern, with debilitating outcomes that carry enormous social costs in the United States of America. Mindfulness-Based Cognitive Therapy (MBCT) is one of the most promising recent developments in the effort to prevent relapse and recurrence of depression;however its dissemination within community mental health or primary care settings is considerably limited. eMBCT, a web-based version of MBCT will be developed and tested so that access to this preventive treatment can be extended to a broader audience of at risk individuals.